Final answer:
Two or more elements joining chemically always form a compound, which has a distinct and fixed composition represented by a molecule with a specific chemical formula.
Step-by-step explanation:
When two or more elements combine chemically, they form a compound. A compound is a distinct substance composed of atoms of two or more elements joined by chemical bonds. Each molecule of a compound has a specific composition and configuration; for instance, a water molecule always comprises two hydrogen atoms and one oxygen atom, which is denoted by the chemical formula H₂O.
These atoms are held together in a molecule by chemical bonds such as polar covalent bonds, hydrogen bonds, non-polar covalent bonds, and ionic bonds. Therefore, when elements chemically combine, they do not form a chromosome, an atom, or a cell, but rather a compound.